1. Field of the Invention
The present invention relates to a fuel heating type fuel filter device which is suitable for use in vehicles equipped with diesel engines.
2. Description of the Related Art
The fuel used with a diesel engine, i.e., light oil, tends to solidify into a wax-like state when cooled below -10.degree. C., thus tending to cause a blockage in the fuel filter. This clogging obstructs the supply of fuel to the engine, and thus a smooth operation of the engine is not obtained. Accordingly, the fuel must be heated in low temperature conditions. U.S. Pat. No. 4,539,108 and U.K. Patent No. 2140319 disclose constructions in which a heater made of a material having a positive temperature coefficient of resistance is provided in a fuel passage of a fuel filter device, to heat the fuel and thus liquify the wax component in the fuel.
In the above conventional fuel filter device, however, a switch for supplying electric power to the heater is provided separately from the heater, and thus the structure of the device must be large in size.